Previewing the first left of Major League Soccer’s Western Conference final (Sunday, 9 p.m. Eastern), here are the must-knows about the Portland Timbers ahead of their trip to Real Salt Lake:

Portland’s reached another level

The Timbers will go into Sunday’s match unbeaten in 10 — their second double-digit run of that type this season — but if you need something more concrete to measure their progress, consider their season series with Seattle. Portland played their Cascadia rivals five times this year, the first three games playing out as low scoring coin flips: two 1-0s (split between the teams) and a 1-1. In the playoffs, though? Portland was up 2-0 into the 90th minute in Seattle (2-1 final) and 3-0 at one point at JELD-WEN (3-2 final).

In that sense, Portland seems to be improving. Or peaking. Whatever you want to call it, their improvement makes sense. This is a team that was remade in the offseason. Most of their players have yet to complete their first year under their new coach. If Portland’s results have improved at the end of the season, it’s because the team’s taken a natural course. The more they know each other (and what each other’s capable of), the better they perform.

So how relevant is their history with Salt Lake?

Back in 2011, Portland won their first meeting with Real Salt Lake, a 1-0 victory that snapped RSL’s 18-game regular-season unbeaten run. Since, the Timbers are 0-5-3 against Jason Kreis’s team, swept in 2011 before going 0-2-2 this year under Caleb Porter.

Given Portland may be at “another level” (as we claim, above), how relevant is that past? Well, the frequency with which the sides played is hard to ignore. Three hundred sixty minutes isn’t meaningless, even if the final scoreline (9-6, RSL) sees the teams closer than the record may hint.

Caleb Porter (right), seen here with Timbers owner/president Merritt Paulson, see Seattle’s use as a midfield diamond as helpful, given his team’s lack of preparation time for Real Salt Lake. (Photo: AP.)

At a minimum, the results provide a baseline. With the exception of the team’s last regular season meeting in Sandy (4-2, RSL), the games were always close, but even in that game, injuries, absences, and suspensions let to Porter trying a 3-6-1 formation – the only time all year he’d do so. That result can go out the window.

If Portland truly has stepped up this postseason, RSL is close enough for them to catch.

But for that matter, how relevant is Seattle?

The big takeaway from the Seattle series (beyond the final result) is how the Sounders set up. They played a diamond midfield, a shape Portland will also see against RSL.

Caleb Porter:

“So we’re really in a rhythm playing basically (against) a similar system. I think that’s a real key in a quick turnaround.

There’s not a ton of tactical changes that we’re going to have to make. A lot of the same things we will want to exploit against Salt Lake are things we wanted to exploit against Seattle.

I think our guys will have a lot of confidence knowing we just faced a really talented team in Seattle, playing a diamond and now we go face another really talented team playing a diamond.”

The main difference, though: Seattle had been playing the diamond for a matter of weeks. For them, it was the formation that slowed their October collapse. For Real Salt Lake, it’s the formation they’ve mastered. With it, they’ve never finished lower than third in the West over the last four seasons.

Travel; turnaround; altitude

As Saturday’s match in Houston showed, this turnaround is ridiculous. All four conference finalists played mid-week, had two days rest, and are expected to play conference final legs this weekend. On Saturday, the result was a bunch of rubber legs. Don’t expect Sunday’s match to be much different.

Portland and Kansas City have (or, had) the extra challenge of travel, taking a big chunk out of their preparation and recovery time. Add in the fact that the just-above-sea-level Timbers are traveling to Salt Lake — around 4,200 feet high — and Portland had to overcome on more small wrinkle.

The question for Porter is how he manages his squad. At forward, does Max Uruiti or José Valencia get the call over Ryan Johnson? Or was bringing Urruti on for Johnson in Thursday’s second half enough? How long can Diego Valeri go? To what extent are players like Diego Chara, Will Johnson, and Jack Jewsbury going to slow come minute 75? And does the whole team adopt a different approach knowing they’ll be more susceptible to being spent come full time?

Another small factor: Both of Portland’s semifinal legs were played on turf. The recovery time coming off the fake stuff just isn’t the same. Anecdotes about injury frequency or how terrible some turf plays may have become apocryphal, but recovery time on turf versus grass can still be a real issue.

By the end of this match, the Timbers could be dead, flatted by a series of small factors that have stacked up against them.

In his first year in Portland, Will Johnson set career highs in goals, assists, shots, and minutes played. (Photo: Getty Images.)

A different Will Johnson

One year ago, Johnson had just played his last game with Real Salt Lake, his team eliminated in the conference semifinals by the Seattle Sounders. Now the former RSL midfielder, who spent five years in Utah, returns as captain of the team trying to keep the hosts from their second MLS Cup final.

But the change of uniform isn’t the only difference with Will Johnson. The 26-year-old Canadian international set career highs in goals (nine), assists (five), and shots (55). Perhaps not coincidentally, he also played more minutes (2520) than he ever has before.

Yet look around, see all the other players having their best MLS seasons in Portland, and Johnson seems to be one of many players in the right place at the right time. All of Darlington Nagbe (nine) and Rodney Wallace (seven) set career highs in goals, Ryan Johnson (nine goals) was more productive than he’s been since 2009, while Diego Chará was more influential than he was throughout his first two MLS seasons.

So maybe Will Johnson hasn’t changed that much. Maybe his surroundings are bringing the best out of him. Regardless, Johnson (like many of his teammates) is the best year of his career. And in that light, he’s not the same player RSL sent to Portland this winter.